1. Field of the Invention
This invention relates to an apparatus for measuring in a supermarket in a combined manner the weights of various objects, such as various goods to be packaged together, on which goods a predetermined weight is displayed after they have been measured and packaged together.
2. Description of the Prior Art
In a facility, in which a great deal of goods are handled, such as a supermarket, many kinds of goods of predetermined weights are packaged. In order to subject a large quantity of goods to measurement for preparing a plurality of sets of the goods of a predetermined weight and thereafter packaging them, it is necessary that the measurement of the weight of the goods be done accurately and speedily. In order to meet the requirements, a combination measuring apparatus having a so-called circular arrangement using a computing element in a microprocessor has recently been developed and widely employed.
In a generally-used combination measuring apparatus, the parts which will be described later are employed so as to process a large quantity of goods efficiently and increase the accuracy of the combination computation greatly. A plurality of heads, for example, fourteen heads are arranged circularly, and each head is provided with a combination of a pool hopper disposed on the upper side and a measuring hopper disposed on the lower side of and in opposition to the pool hopper. The goods to be measured are supplied from the upper central portion of the apparatus into a pool hopper via a distribution table and an electromagnetic feeder opposed to the relative head, so as to hold the goods in the pool hopper. When the measuring hopper disposed below this pool hopper has become empty, a discharge plate of the pool hopper is opened for a predetermined short period of time to feed the goods to be measured into the measuring hopper and then close the discharge plate.
In each hopper, into which the goods have been fed, the weight of the goods is detected by a weight detector, such as a load cell, and a detected signal is inputted into a computing element in a microprocessor to determine a combination of heads, in which the weight of the goods is closest to a set target level. The discharge plate of the measuring hopper in each selected head is opened for a short period of time to discharge the goods therefrom, and the discharge plate is then closed. Through such a process, the goods are subjected to weight measurement to prepare a plurality of sets of the goods of a weight substantially equal to the set target weight.
Recently, in which the circulation market has become active, the speedup of the processing of goods has strongly been demanded, and, therefore, the weight measuring process has also required to be carried out at a higher speed.
However, the construction, which obstructs the high-speed processing of goods, of the above-described conventional combination measuring apparatus has often become an issue.
In the above-described conventional combination measuring apparatus, a dropping system is employed in all of the steps of throwing goods to be measured into the upper central portion of the apparatus, supplying the goods from the electromagnetic feeders to the respective heads, feeding the goods from the pool hoppers in the heads to the corresponding measuring hoppers, and transferring the weight-measured goods from the measuring hoppers to a subsequent packaging stage. There is naturally a limit to the employment of the dropping system which is different from a forcible transfer system. In the dropping system, the goods are dropped slidingly with respect to the surface of the parts thereof, so that the dropping speed of the goods decrease due to the friction occurring between the goods and the mentioned surfaces. This prevents the speedup of the weight-measuring operation.
In order to minimize the friction occurring in a step of slide-dropping the goods to be measured, it is necessary to reduce the dropping distance, i.e. the height of a part from which the goods are dropped and the distance between this part and the part onto which the goods are dropped therefrom. However, in this conventional apparatus, the mechanism for opening and closing the discharge plates of the pool hopper and measuring hopper includes a motor, a cam link means and a crank system, which are provided for each head in the central portion of a frame of the apparatus. Therefore, the lateral distances between the center of the apparatus and the pool hopper in each head and the discharge plates cannot be reduced. As a result, the friction between the goods and the above-mentioned parts cannot be minimized. Moreover, the angles of inclination of inclined surfaces of these parts is inevitably left acute, and the heights thereof cannot be reduced.
Consequently, the height of the combination measuring apparatus increases, and various operating mechanisms therein are necessarily disposed in high positions, so that the height of the center of gravity of the apparatus increases. Hence, the apparatus becomes unstable, and the suppressing of vibration of the apparatus can be done to only a limited extent.
It is important to increase the measuring speed without decreasing the measuring accuracy in a calculation cycle in the combination measurement. The detection of the weight of goods by means of a load cell, the combination computation and the inputting of a detected signal and a control signal can be carried out electrically and statically at a high speed. However, the means for opening and closing the discharge plates of the pool hoppers and measuring hoppers are accompanied by mechanical operations, so that the reduction of measurement time is restricted. This causes the time for processing goods to be prolonged, and the parts of the apparatus to wear earlier. As a result, after the apparatus had used for a long period of time, it would rattle. This causes a decrease in the measuring accuracy and the working life of the apparatus and troubles in the repairing operation
Since these mechanical operating parts are provided on the upper portion of the machine frame as mentioned above, they are apt to wear early due to the resonance caused by the mutual vibrations thereof, and the measurement accuracy of the apparatus decreases early.